Is Lack of Sleep the Cause of Overeating? The Often Overlooked "Sleep Time" in Dieting

Is It True That Staying Up Late Makes You Gain Weight? Deciphering the "1.64 Points of Body Fat in One Hour" Statistic

Even if you eat less, walk as much as possible, and weigh yourself regularly, you might not see the results you want and start wondering if your willpower is weak.

In such cases, it's worth reconsidering your daily sleep habits. Are you cutting into your sleep time by watching videos or using your smartphone late into the night?

On October 5, 2026, Germany's FOCUS online discussed the relationship between late bedtimes and body fat. While considering sleep as part of weight management is useful, the numbers presented in the article should be read with caution.

What Does "1.64 Points in One Hour" Represent?

The focal point is a study published in the 2021 edition of the academic journal Nutrients, which targeted 83 overweight and obese adults. Researchers examined the relationship between their recorded diet, sleep, physical activity over seven days, and measured body fat percentage.

The "1.64" figure in the abstract of the paper represents a statistical association between going to bed one hour later and having a body fat percentage that is 1.64 percentage points higher.

This does not mean that if you go to bed one hour later tonight, your body fat percentage will increase by 1.64 points the next morning. It was not an experiment where participants changed their bedtime to confirm fat gain.

As this study compared the timing of daily life and body fat percentage, causation cannot be determined. The subjects were also overweight and obese adults, so the same numbers may not apply to people of all ages and body types.

Rather than a number to calculate the "cost of staying up late," it should be seen as a prompt to consider the timing of sleep and meals.

Consider Bedtime and Sleep Duration Separately

Going to bed at 11 PM and waking up at 5 AM is different from going to bed at 1 AM and waking up at 9 AM in terms of both bedtime and sleep duration. Treating these two scenarios as simply "late sleepers are unhealthy" overlooks important differences.

Similarly, you cannot evaluate people who have limited sleep time due to work and those who have ample time to sleep based solely on the clock.

What we should consider from this report is not a boundary line of "what time should I go to bed to avoid gaining weight," but rather how sleep time is secured in one's life.

Lack of Sleep May Lead to Increased Food Intake

When considering the relationship between sleep and weight management, experiments that actually change sleep duration are informative.

A study published in 2011 found that under conditions of reduced sleep, daily energy intake was about 300 kilocalories more than under normal sleep conditions. Meanwhile, there was no significant difference in total energy expenditure.

The FOCUS article mentions a study from Columbia University stating "energy expenditure increased by about 300 kilocalories," but in the relevant study, it was energy intake, not expenditure, that increased. This distinction is crucial for understanding the relationship with weight.

It is not appropriate to dismiss the relationship between lack of sleep and overeating as mere lack of discipline. However, it is also important to note that not everyone will overeat the same amount based on short-term experimental results.

Does Extending Sleep Change How We Deal with Appetite?

There are also studies that investigate from the opposite perspective.

A randomized controlled trial published in JAMA Internal Medicine in 2022 involved an intervention to extend sleep among 80 overweight adults who typically slept less than 6.5 hours.

The group that received individual sleep guidance slept an average of about 1.2 hours longer than the control group and consumed about 270 kilocalories less per day.

This result suggests that securing sleep may support dietary habits. However, the intervention lasted two weeks and does not prove that "anyone will lose weight by sleeping longer" or that "diet and exercise can be ignored."

Sleep is not a magical weight loss method. Nonetheless, it is worth reconsidering as a condition for continuing dietary management.

On Social Media, Concerns About Both Hunger and Sleep

On the overseas bulletin board-style social network Reddit, in the weight loss community "r/loseit," the relationship between sleep and appetite is a hot topic.

The following are not direct responses to the FOCUS article but summaries of public posts on the same theme. These are personal experiences and do not represent research results or public opinion as a whole.

A post titled "Anyone else notice they are hungrier if they don’t sleep well?" describes the experience of feeling hungrier earlier on days when sleep was poor, even when eating the same amount. Replies mention not only the intensity of hunger but also a change in the types of food cravings.

Another post, "How to not overeat when you’re overtired," expresses the difficulty of sticking to set calorie intake when chronically sleep-deprived.

Meanwhile, a post titled "How do you guys deal with bad sleep due to hunger?" discusses the struggle with nighttime hunger and deteriorating sleep quality during weight loss efforts.

These posts reveal that simply advising "don't eat at night and go to bed early" is insufficient. Some people find it hard to manage appetite due to lack of sleep, while others disrupt their sleep by cutting back on food too much.

The takeaway from these experiences is not a one-size-fits-all solution but a perspective that considers changes in hunger and sleep, not just weight.

In Japan, Start by Securing "Necessary Sleep"

The Ministry of Health, Labour and Welfare's "Sleep Guide for Health Promotion 2023" recommends that adults secure at least six hours of sleep as a guideline.

This does not mean "six hours is sufficient for everyone." There are individual differences in the necessary length, and the "feeling of restfulness" upon waking is also emphasized.

When organizing your lifestyle, consider getting sunlight in the morning, reviewing the use of strong lights and smartphones at night, and paying attention to meals and caffeine close to bedtime.

One suggestion is to jot down the times you sleep and wake, daytime drowsiness, and moments of hunger for a few days. This can help you reflect on your lifestyle, such as whether staying up late coincides with snacking the next day.

For those whose sleep time is limited due to work, childcare, or caregiving, it may not be something that can be resolved through individual effort alone. The focus should be on considering adjustments or support to secure rest time, not self-blame.

Before further reducing food intake, check how much you are postponing sleep each night. Adding "a lifestyle that allows for adequate rest" to your weight management plan is a step towards maintaining it without strain.

Source URL

1. FOCUS online (October 5, 2026)
   A report introducing the relationship between late bedtimes and body fat.
   https://www.focus.de/gesundheit/gesundleben/jede-stunde-messbar-spaetes-schlafengehen-erhoeht-den-koerperfettanteil_4f602761-fa45-42c4-bfad-e233a261a360.html

2. Thomas et al. "Later Meal and Sleep Timing Predicts Higher Percent Body Fat"
   The original paper investigating the relationship between meal and sleep timing and body fat percentage in 83 adults. The "1.64 points" indicates an association with sleep end time.PubMed
   https://pubmed.ncbi.nlm.nih.gov/33383648/

3. St-Onge et al. "Short sleep duration increases energy intakes but does not change energy expenditure in normal-weight individuals"
   An experiment where energy intake increased by about 300 kilocalories with short sleep duration, with no significant difference in energy expenditure.PMC
   https://pmc.ncbi.nlm.nih.gov/articles/PMC3142720/

4. Tasali et al. "Effect of Sleep Extension on Objectively Assessed Energy Intake Among Adults With Overweight in Real-life Settings"
   A randomized controlled trial where extending sleep resulted in a reduction of daily energy intake by about 270 kilocalories compared to the control group.PubMed
   https://pubmed.ncbi.nlm.nih.gov/35129580/

5. Ministry of Health, Labour and Welfare "Sleep Guide for Health Promotion 2023"
   Official document on adult sleep duration, restfulness, and lifestyle/environment creation.mhlw.go.jp
   https://www.mhlw.go.jp/content/001305530.pdf

6. Reddit "Anyone else notice they are hungrier if they don’t sleep well?"
   Experiences about changes in hunger and food cravings on days of poor sleep. Summary of publicly available parts confirmed through search.reddit.com
   https://www.reddit.com/r/loseit/comments/1dn7d0e/

7. Reddit "How to not overeat when you’re overtired"
   Discussion about the difficulty of maintaining calorie intake when fatigued or sleep-deprived. Summary of publicly available parts confirmed through search.reddit.com
   https://www.reddit.com/r/loseit/comments/szmyvr/

8. Reddit "How do you guys deal with bad sleep due to hunger?"
   Discussion about nighttime hunger and worsening sleep during weight loss. Summary of publicly available parts confirmed through search.reddit.com
   https://www.reddit.com/r/loseit/comments/qup9mv/